Critical severity · published Sep 21, 2025
CVE-2025-6544
Deserialization Vulnerability in h2oai/h2o-3
9.8
CVSS
0.9%
EPSS
No
On KEV
Description
A deserialization vulnerability exists in h2oai/h2o-3 versions <= 3.46.0.8, allowing attackers to read arbitrary system files and execute arbitrary code. The vulnerability arises from improper handling of JDBC connection parameters, which can be exploited by bypassing regular expression checks and using double URL encoding. This issue impacts all users of the affected versions.
CVSS vector
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.9% · higher than 60% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
H2
h2oai/h2o-3 · h2oai
before 3.46.8 · source: vendor
H2
H2o · H2o
3.0.0.2 through 3.46.0.8 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2025-6544
CVE.org
https://www.cve.org/CVERecord?id=CVE-2025-6544
Patch
https://github.com/h2oai/h2o-3/commit/0298ee348f5c73673b7b542158081e79605f5f25
Exploit
https://huntr.com/bounties/53f35a0f-d644-4f82-93aa-89fe7e0aed40
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